This invention relates to methods and apparatus for delivery of medicament to the respiratory system of a patient. In particular, the invention relates to apparatus and methods of this type for use in association with a nebulizer.
It is known to use a nebulizer to create an aerosol of medication for delivery into the respiratory system of a patient. Typically the medication is placed in a cup which is held over a reservoir of buffer water. A piezoelectric element is vibrated ultrasonically under the buffer water transferring energy to the water, thus causing an aerosol to be formed in the medication cup. Baffles are provided between the medication cup and the airway in an attempt to ensure large particles of medication rain out on the filter and drip back down into the medication cup.
These nebulizers suffer from a number of disadvantages. In particular, medications have a range of different viscosities, however particle generation is not consistent across the range. Thus the medication particle size is not accurately controlled and a broad range of particles pass into the patient airway. Nebulized medication which rains out on the filter drips back into the cup only to be nebulized again. This may degrade or destroy the medication.
The medication in the cup is directly exposed to the airway. Therefore the nebulizer must be maintained substantially horizontal at all times to prevent medication spilling out into the patient airway. Also the ventilator pressure will be lost when the medication cup is removed to refill it.
This method of aerosol generation requires a relatively large amount of energy, the response time of aerosol generation is thus large. A considerable amount of heat is generated during use of the nebulizer, therefore to prevent patient discomfort or injury the nebulizer is placed away from the patient. However this necessitates a long inhalation tube between the nebulizer and the patient, increasing drug loss through rain out along the inhalation tube, and further increasing the response time to patient inspiration. Further, the generated heat degenerates the medication, which can be particularly harmful to protein based drugs.
Hence, this invention is related to apparatus and techniques for delivery of medicament to the respiratory system of a patient.